This invention relates to a printhead writer assembly. Although not limited thereto, it is particularly usable in mounting a linear LED array and its lens with respect to an image member.
U.S. Pat. No. 4,715,682 and U.S. Pat. No. 4,728,981, issued Dec. 29, 1987 and Mar. 1, 1988, respectively, to K. C. Koek et al, shows an LED printhead assembly. The assembly includes an elongated focusing device, such as a linear gradient index lens array, and an elongated linear source of radiation. The radiation source includes a conventional linear array of LED's on a suitable support with a transparent faceplate and a cooling mechanism. The lens array (sometimes called the "lens") is fixed to a lens support which, in turn, is mounted in a housing. One end of the lens support is fixed to the housing and the other is allowed to move against a spring to allow for thermal expansion. The housing includes a mechanism for mounting the LED printhead and the lens with respect to each other and also with respect to a web type image member.
U.S. Pat. No. 4,928,139, issued May 22, 1990 to Barton et al shows an LED printhead assembly in which a bracket receives the linear LED array and a support for the lens. The factory positioning of the lens with respect to the LED array is accomplished by oversized holes in the bracket and screws which fit into the lens support through the oversized holes. Movement within the holes allows movement of the lens during accurate positioning. Oversized washers on the screws are adhesively fixed to the portion of the bracket surrounding the holes once the desired position between the LED array and the lens is achieved. Thermal expansion between the lens support and the bracket is handled by sliding movement between the screws and the adhesively fixed washers.
U.S. Pat. No. 5,036,339, granted to Hediger Jul. 30, 1991, shows thermal expansion compensation structure in which a lens support is mounted to float in two directions while maintaining its distance from the LED array.
U.S. Pat. No. 4,821,051, Hediger issued Apr. 11, 1989, and U.S. Pat. No. 4,913,526, Hediger issued Apr. 3, 1990, show a thermal expansion compensation structure in which the lens support is fixed in the middle and allowed to expand in both directions. See also U.S. Pat. No. 4,896,168, Newman et al issued Jan. 23, 1990.
U.S. Pat. Nos. 4,926,198, issued May 15, 1990 and U.S. Pat. No. 4,928,119, issued May 22, 1990, both to Barton and Walker, show an LED printhead assembly having four bearing surfaces. The bearing surfaces are urged against a pair of cylindrical surfaces coaxial with a roller which backs a web type image member. See also, U.S. Pat. No. 4,703,334, issued Oct. 27, 1987 to Mochimaru et al.; U.S. Patent No. 4,278,982, granted July 1981 to Cholet, U.S. Pat. No. 4,780,730, granted October 1988 to Dodge, and U.S. Pat. No. 4,427,284, issued January 1984 to Dannatt.
Most of the above assemblies work with a web image member, for example, a photoconductive image member. Positioning of the lens and LED array with respect to the web image member is accomplished by contact with a backing roller or other web support directly or through intermediate machine structure. Basically, the positioning structure goes around the image member to whatever is backing the web.
U.S. Pat. No. 4,806,991, issued Feb. 21, 1989 to Guslits, is representative of a number of structures showing mounting of development and other stations with respect to an image member. In this reference a backing roller is moved into a web to push it toward a properly spaced position with respect to an image member.